Grendizer: Getter Robo G - Great Mazinger Kessen! Daikaijuu

Mecha

Takes place after the final defeat of the Dinosaur Empire and the death of Musashi Tomoe in the original Getter Robo series. Dr. Saotome, creator of Getter Robo, fears that the peace the Getter Robo team has won will be short lived and that an even greater enemies would appear. Dr. Saotome's fears are justified when the militaristic Hyakki (or "Hundred demons") Empire appears, but Dr. Saotome is prepared with the creation of an even more powerful Getter Robo, Getter Robo G and a new Getter Robo base. Also with Musashi Tomoe dead, Dr. Saotome needs a third pilot which he finds in baseball player Benkei Kuruma. (Source: Wikipedia)

Mecha

Duke Fleed is a survivor of the Fleed Planet who is escaped to the Earth, onboard a mysterious "spaceship", where is raised by Dr. Umon as his adoptive son, and known as Daisuke Umon. Years after his arrival, he's faced with the threat of King Vega and his army, who want to conquer the Earth. With his friends Koji and Hikaru (and later his younger sister Maria Grace), Duke decides to fight back using his best weapon - the almighty Grendizer.

Mecha

A manga comic book and anime television series by manga artist Go Nagai, made as a direct continuation of the successful Mazinger Z series. It was aired on Japan in 1974, immediately following the end of the first Mazinger series.

Action / Comedy

The story revolves around a new team of "Toei robot girls" named "Team Z" that is made up of three girls based on Toei's Mazinger Z franchise: Mazinger Z, Great Mazinger, and UFO Robot Grendizer. Usually they perform in activities around Nerima ward in Tokyo to raise the awareness of the promising future energy source "Photon Power" (koushiryoku). However, there are times when "Mechanical Beast" team of girls emerge from the "Subterranean Empire" and attempt to steal the energy. Thus "Team Z" has to battle them to prevent this, though sometimes they just go and beat up the "bad girls" to relieve stress.

Action / Mecha

Go Nagai crossover movie.

Mecha / Sci-Fi

Alien invaders take over Great Mazinger who is at the entrance of a museum next to Mazinger Z as symbols of peace. Grendizer fights the evil invaders and Great Mazinger is recovered. When the Vegan empire dispatches a new general to oversee the takeover of Earth, he quickly manages to capture Koji Kabuto and, learning of Great Mazinger through interrogation, quickly commandeers it from a museum where it was kept as a symbol of peace. It is now up to Duke Fleed aboard Grendizer to stop humanity's former defender from becoming its destroyer. (Source: Anime News Network)